The operation, running from February 2014 to April 2017, cost $177,349 of taxpayers' money. It's not known how many people were spied on, but hundreds of people were involved in protests following the Christchurch quakes.

Cam Preston, a father, chartered accountant, and victim of the Christchurch earthquake, was also deemed a "threat" who needed to be monitored.

Cam Preston.
Photo credit: Newshub.

Mr Preston was one of the main targets of an operation set up by Southern Response using "protection agency'' Thompson and Clark Investigations.

The security firm's 'security risk management proposal' warns of "the threat of a sustained, directed campaign by issue-motivated groups and individuals of either legal or illegal nature."

"Situational awareness and keeping a rod in the water - to me they just seem like fancy terms for spying."

Mr Preston had certainly been persistent, sending emails almost daily - hundreds in total. He was protesting, fighting to get his claim settled.

Once, he shouted at the Southern Response chief executive.

"I'm stuck in an earthquake-damaged home with a family that wants to move on with their lives, and when your insurance company doesn't respond to you, there's actually nothing else you can do," he told Newshub.

He was also helping organise a group of claimants taking a legal case against Southern Response.

The exact spying tactics used by Thompson and Clark have been kept secret, but the organisation has previously been caught snooping on and even infiltrating environmental groups.

The spying came as a shock to Mr Preston's wife, Wendy.

"You don't know how they're spying on you. Is it someone looking at you? I mean, it seems silly to even say it.

"Is there something in your house? Are they following you around? Are they taking photographs of you? I don't know. What are they doing?"

The Preston family in their garden.
Photo credit: Newshub.

An email from Thompson and Clark to Southern Response, obtained by Mr Preston under the Official Information Act, shows the private investigators keen to get police involved.

"Yes, we believe pressure should go on police to talk to [blacked out name]".

An email obtained under the Official Information Act.
Photo credit: Newshub.

The name was obviously Cam Preston, because a week later, police hit him up.

"You know, we're a normal law-abiding family. To have the police turn up at your doorstep can be a bit of a shock, and if they're trying to rattle myself and my family, well they did."

A police report shows Southern Response told police Mr Preston was a risk to several staff. It said there its "concerns are a repeat Ashburton WINZ incident". That's a reference to the attack in which two Work and Income staff members were shot dead.

"To spy on people, and to paint my husband, and the father of my kids, as somebody who is akin to a WINZ shooter? It's just.. no, you can't do that to normal people. How has this happened?" Ms Preston said.

"It's New Zealand, not Russia. It's just not the Kiwi way. It's not how we do things in New Zealand, and that's probably the reason I'm talking to you now.

"I've got nothing to gain from any of this, apart from to ensure that my family, my kids grow up in a country where this sort of thing doesn't happen," Mr Preston said.

They are ordinary Kiwis subjected to extraordinary spying.

Following inquiries from Newshub, the State Services Commissioner announced an official inquiry will be launched.

SSC Peter Hughes says the evidence raises questions around compliance and with standards of integrity and conduct for state servants.

Responses

SSC state services commissioner Peter Hughes

​"The material I have seen raises questions around compliance with standards of integrity and conduct for State servants. Those questions need to be answered."

Southern Response Board chair Ross Butler:

"Southern Response was acting in response to an escalating level of threatening and aggressive behaviour and communications from customers towards staff, the Chief Executive, directors, and the Chairman."

Thompson & Clark

"Thompson & Clark do not disclose our clients nor operations we can however advise that as licensed private investigators we operate within the law and in compliance with industry standards and guidelines."